Network operators running dynamic routing or label distribution protocols need to monitor service interruptions caused by routing protocol changes over their network. To monitor the “reaction” of their network following such service interruptions, network operators need to measure the length of the interruption when a change occurs.
For the purposes of this discussion a service interruption time is divided into the following components:
1. A protocol convergence time, which is the time taken for all instances of a routing protocol running on routers in a network to update their Routing Information Bases (RIBs) and propagate any routing changes to other peer routers;
2. In a Multi Protocol Label Switching (MPLS) network, there is an additional protocol convergence component attributable to the time taken to update all Label Switch Router (LSR) label distribution protocol binding tables and propagate any label changes to other peer LSRs;3. Forwarding Information Base (FIB) Insertion time, which is the time it takes for each router to install the new routing protocol information into its forwarding tables to allow it to send packets to a destination; and4. In an MPLS network, there is an additional component to the service interruption attributable to Label Forwarding Information Base (LFIB) update time—the time it takes a Label Switch Router (LSR) to update its Forwarding Equivalence Class (FEC) forwarding table.
Already known in the art are commercial active monitoring products measuring routing protocol convergence time only. The method used for measuring routing protocol convergence consists of injecting a route into a network at a specific time from one location in the network and to record the time it is received at other location(s) in the network. This method gives a partial measure of protocol convergence time since it does not measure FIB or LFIB Update. This technique also requires multiple devices to actively or passively participate with the routing protocol.
FIB/LFIB update time is a relatively speedy process which is typically measured in range of milliseconds to 100 s of milliseconds. Protocol convergence time can vary widely depending on the specific protocol and the characteristics of the network on which the protocol is being used. For networks where the protocol convergence time is greater than one or two seconds, the FIB insertion time is inconsequential; however, on modern networks engineered for fast convergence, the protocol convergence can be equal to or less than the FIB insertion time. On these networks knowing the combined protocol+FIB insertion convergence time is important in assessing network performance.
US Patent Application US 2007/0008953 describes a technique to passively measure the effects of randomly occurring routing protocol events on network traffic exchanged between two or more devices in the network. If traffic exchanged between devices is delayed, lost, or corrupted, these impairments are correlated with routing protocol events being passively monitored. This technique allows the impact of actual network routing events to be measured. However, this technique does not enable the periodic monitoring of network and protocol routing convergence to be measured and a baseline of performance to be established against which measurements can be compared.
The Internet Engineering Task Force (IETF) has published a series of Request for Comments (RFCs) and Internet Drafts which discuss the terminology and methods to benchmark various aspects of network convergence. While the terminology these documents introduce is relevant and used herein, the focus of these documents is laboratory testing of a device or a network configuration of multiple devices; the techniques do not lend themselves directly to automated non-disruptive testing required for monitoring production networks.
It is believed that there is a need for a method embodied in a network element that can measure, in an automated and non-disruptive way, the length of service interruption when there is a protocol change in a network, such as a routing protocol change or a label distribution protocol change. There is also a need for a method and network element that can measure service interruptions more accurately than currently utilized techniques, by including in the measure of the service interruption the FIB/LFIB Update time. It would also be desirable to have a method and network element for monitoring service interruptions that can be implemented on a single network element for reducing costs comparatively to techniques requiring at least two and often more devices to participate in the protocol.